1. Field of the Invention
This invention relates to a kinematic universal coupling, and more particularly to a coupling for rotary shafts which is capable of transmitting a torque even when the centers of the shafts on the driving side and the driven side are not coincident with each other.
2. Description of the Prior Art
Among the couplings used for the above-described usage, there is what is called Oldham's coupling. In such coupling, straight grooves passing the center are provided in opposed coupling members, and pieces having on the front and back sides thereof straight projections perpendicular to each other are so combined that the grooves are perpendicular to each other. In the coupling of this type, however, when it rotates with two eccentric shafts coupled together, the center of gravity of the abovementioned pieces rotates on the circumference of a circle whose diameter is the center distance between the two shafts and therefore, when the rotational speed is high, large vibration occurs and the coupling cannot be used. On the other hand, when the amount of eccentricity between the two shafts is very small, use is sometimes made of a flexible shaft coupling using rubber or a spring, but the stress created in the coupling portion is high and the transmission efficiency is low and sometimes, such coupling lacks uniform speed transmission.